Re: Advantage(s) of static over dynamic nftables sets?

[Florian Westphal <fw@strlen.de>]

Frank Myhr <fmyhr@fhmtech.com> wrote:
> > > I suppose intervals are more efficient than an equivalent group of single
> > > elements?
> > 
> > Memory-wise yes, performance-wise no.
> 
> Also good to know.
> 
> > > Is a concatenation like ipv4_addr . inet_service as efficient as a pure data
> > > type with the same number of bits?
> > 
> > Yes, as it makes no difference for the storage.  The kernel doesn't know
> > what its storing, it only knows the size of the element.
> > 
> > It does store a 'type' information, but that is only used by nftables
> > so it knows how to format the elements when listing the ruleset.
> 
> Thanks for confirming, and for all of your detailed answers.
> 
> If you find the time (and if it's comprehensible to a non-kernel
> programmer): How does a dynamic set change the above situation? Does it use
> a hash table for everything?

Yes, dynamic set always uses 'rhashtable' backend, thats the only type
that supports insertion from the packet path.

We have 3 hash tables, a simple one for 32bit keys, one for static sets
(table size decided at creation time) and rhashtable (table size is
auto-resized as needed).